There is suggested a technology of coating a bioactive ingredient for fertilizers, pesticides and the like with a coat film, thereby controlling elution appropriately, so as to cause elution thereof at given period according to the growth of plants (see, e.g., JP10-029886A, JP11-005704A).
Recently, enhanced attention is paid to easily degradable resins for thoughtful consideration for the environment. With coated granules of a bioactive substance, however, it is difficult to control elution using an easily degradable resin as a coat film so as to elute a bioactive component at given period.